For example, top-emission type display devices using organic electro-luminescence (EL) light-emitting elements, inorganic EL light-emitting elements, or the like, an element substrate in which the light-emitting elements are disposed and a sealing substrate facing the element substrate are provided. Light emitted from the light-emitting elements passes through the transparent sealing substrate and is observed. For example, when each light-emitting element emits white light, the light emitted from each light-emitting element passes through color filters formed in the sealing substrate and is observed as light of the color of each pixel. Further, when the light-emitting elements emit light with colors of respective pixels, such as red, green, and blue, color filters are also used in some cases to improve color purity.
In the foregoing sealing substrate (also referred to as a color filter substrate), a light-shielding member called a black matrix is formed at a position corresponding to a boundary between pixel regions in order to improve contrast. A technology for the black matrix is disclosed in, for example, PTL 1. According to the technology of PTL 1, in order to suppress a diffraction phenomenon of light occurring in a boundary between a transmission region of a color filter and the region of a black matrix, a gradient of an optical density is formed in the transmission region.